IACR News item: 19 March 2015
Junji Shikata
ePrint Report
Specifically, the contribution of this paper is as follows. We first derive a new lower bound on entropy of secret-keys, and it is described in terms of \\R entropy. Next, we define that a good A-code having non-uniformly random keys is the one satisfying equality of the bound, and it is characterized by the min-entropy (a special case of \\R entropy). Furthermore, we introduce the classification methodology for A-codes which are realizable from a biased key-source. This classification is performed by using a mathematical tool, i.e., a group action on the set of authentication matrices. By this analysis, we can understand what kind of A-codes is actually constructable.
Finally, we design how to construct good A-codes having 1-bit messages from von Neumann sources. We also show that our construction methodology is superior to the one by applying von Neumann extractors and the traditional optimal A-code constructions. Although the case of 1-bit messages may be restricted, however, this case is simple and we believe that a general case will develop from this simple case.
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